This invention relates generally to sealed compressor housing and specifically to a sealed compressor housing including vibration dampening features to reduce audible noise emission.
Refrigerant compressors typically include a compressor pump unit driven by a motor within a sealed housing. In such compressors, refrigerant flows over the motor driving the compressor pump to cool the motor during operation. Therefore, the sealed housing must provide a fluid tight seal. Most housings are constructed from upper and lower shells attached to corresponding ends of a center cylindrical shell. The motor and compressor are secured within the center shell.
A scroll compressor is one common type of compressor used for commercial and residential applications. Scroll compressors operate by trapping refrigerant within compression chambers formed between interfitting scrolls. Each scroll has a generally spiral wrap extending from a base. Typically, one of the scrolls is an orbiting scroll and the other is non-orbiting. The motor drives the orbiting scroll relative to the non-orbiting scroll to progressively reduce the volume of the compression chambers, thereby compressing the refrigerant.
The compressor and motor create undesirable vibrations and noise. Typically, the motor and compressor operate at a constant speed to emit noise within a known operating frequency range. Noise emanating from the motor and compressor resonates within the sealed housing, thereby increasing the magnitude of noise. Many sealed housings are constructed such that a resonance frequency of the sealed housing is within the operating frequency range of the motor and compressor. The configuration and materials used to construct the sealed housing determines the resonant frequency, and when a sealed housing is constructed such that the resonance frequency is within the frequency range of the motor and compressor, the sealed housing amplifies noise emanating from the motor and compressor.
It is known in the art to modify the construction of the sealed housing to minimize the amplification effects of the sealed housing. Typically, such sealed housings include asymmetrically orientated surfaces disposed within the sealed housing that reflect overall sound waves in a manner to prevent subsequent sound waves from building upon each other to increase noise emanating from the sealed compressor. The asymmetrical shape prevents sound waves from reflecting between two facing surfaces of the sealed housing to minimize resonance within the sealed housing. Asymmetrically shaped components for a sealed compressor increase manufacture and assembly costs to outweigh any noise improvements.
For this reason, it is desirable to design a sealed compressor housing with features that minimize the resonance effects of the compressor and motor to reduce noise emission without prohibitively increasing cost and complicating assembly.
An embodiment of this invention is a sealed compressor housing with features that attenuate resonant effects of the sealed housing to reduce noise emission.
The disclosed sealed compressor of this invention includes a scroll compressor driven by a motor mounted within a sealed housing. The sealed housing includes a center shell section extending between first and second ends and upper and lower shells attached at the first and second ends. The lower shell has a generally square shaped outer periphery with four mounting feet extending diagonally from each of the corners. The lower shell has a predetermined amount of material removed for attenuating vibrations and noise within an operating frequency range of the compressor assembly. The removal of material within the lower shell affects the resonance frequency at which the sealed housing amplifies noise from the motor and the compressor. In one embodiment, material is removed from the skirt width to make it smaller. The width of the skirt relative to the lower shell shifts the resonance frequency of the sealed housing outside the operating frequency range of the motor and compressor. Adjustment of the resonance frequency of the lower shell reduces overall sound emission of the compressor assembly at any frequency, but the greatest noise reduction is obtained for frequencies within the operating range of the motor and compressor. In the first embodiment of the lower shell, a skirt width no more than four and preferably no more than three times the thickness of the sheet material used forming the lower shell. This configuration resulted in a noise reduction of between 3-5 decibels. In this embodiment, the thickness of the lower shell is approximately 3.5 mm and the skirt width 10 mm.
In another embodiment of the lower shell, notches provided in the skirt changes the resonance frequency of the lower shell. The notches in this embodiment are preferably cut from the skirt in a length selected to be of a particular proportion relative to the total width of the lower shell. In one embodiment, the notch includes radial cutouts at each end, and the notches are positioned symmetrically on each of the four sides of the lower shell.
In another embodiment of the lower shell, the notches are also arranged on each of the four sides of the lower shell, but are instead arranged asymmetrically about the perimeter of the lower shell. The asymmetric arrangement of the notches increases the magnitude of the resonance frequency required to excite the sealed housing, further attenuating audible noise emitted from the sealed housing.
In still another embodiment of the lower shell, a cutout disposed on the top surface changes the resonance frequency of the sealed housing. In this embodiment, the dampening opening is disposed at each corner of the lower shell near each of the mounting feet.
The noise attenuating features of the lower shell disclosed in the various embodiments of this invention change the rigidity of the lower shell to shift the resonance frequency of the sealed housing away from the frequency at which the motor and compressor operate to reduce audible emissions from the sealed compressor. The reduction of audible emissions is accomplished by the adjustment of features on the lower shell at a low cost and without additional assembly steps.